102 research outputs found
Phytofiltration of arsenic and cadmium from the water environment using Micranthemum umbrosum(J.F. Gmel) S.F. Blake as a hyperaccumulator
No full textArsenic (As) and cadmium (Cd) pollution in water is an important global issue. Phytofiltration is an eco-friendly technology that helps clean up pollutants using ornamental plants, such as Micranthemum umbrosum (J.F. Gmel) S.F. Blake. After a seven-day hydroponic experiment, M. umbrosum removed 79.3–89.5% As and 60–73.1% Cd from 0 to 1.0 μg As mL–1 and 0.3 to 30.0 μg Cd mL–1 solutions, respectively. For As treatment, root to stem and stem to leaf translocation factors greater than 1.0 indicated that accumulation of As in leaves was large compared to that in stem and roots. However, the accumulation of Cd in roots was higher than that in the leaves and stem. In addition, M. umbrosum completely removed Cd within three days from 0.38 to around 0 μg mL–1Cd in the solution when the plant was exchanged daily. Bio-concentration factors (2350 for As and 3027 for Cd) for M. umbrosum were higher than for other As and Cd phytoremediators. The results show that M. umbrosum can be an effective accumulator of Cd and a hyper-accumulator of As, as it can lower As toxicity to a level close to the limit recommended by the World Health Organization (0.01 μg As mL–1
Potential of Micranthemum umbrosum for phytofiltration of organic arsenic species from oxic water environment
No full textArsenic (As) is a toxic and carcinogenic metalloid that causes various hazards to human health. Phytofiltration is a more eco-friendly and green approach than chemoremediation, or other traditional technologies, for removing As from aquatic environments. Recently, Micranthemum umbrosum was shown as a promising candidate for phytofiltration of inorganic As species. This work examines the potential application of M. umbrosum to phytofiltration of organic As species, such as monomethylarsonic acid (MMAA, CH5AsO3) and dimethylarsinic acid (DMAA, C2H7AsO2), from oxic water environments. M. umbrosum plants were grown in two test concentrations of MMAA and DMAA, or a control, in a hydroponic experiment. After seven days, leaves accumulated 90 +/- 3.2 and 48 +/- 1.6 A mu g As g(-1) (oven dry basis) from 1 A mu g As mL(-1) of water added from MMAA and DMAA, respectively. Bioconcentration factor values and translocation factor values were always greater than 1.0, indicating that M. umbrosum was a good As accumulator and that leaves accumulated significantly higher amounts of As than stems and roots. Analysis of macro- and micronutrient data showed that M. umbrosum had higher resistance to organic As treatments than the control. These results confirm the potential application of M. umbrosum for phytofiltration of organic As from contaminated oxic water environments
Preparation and characterization of chitosan–caboxymethyl-β-cyclodextrin entrapped nanozero-valent iron composite for Cu (II) and Cr (IV) removal from wastewater
No full textThe entrapment of Fe0 nanoparticles within a chitosan–carboxymethyl β-cyclodextrin complex, a nontoxic and biodegradable stabilizer, yields chitosan–Fe0 nanoparticle–carboxymethyl β-cyclodextrin beads that are 2.5 mm in diameter and contain 50% iron by weight. The complete disappearance of Cr (VI) and Cu (II) may involve both physical adsorption and reduction of Cr (VI) to Cr (III) and Cu (II) to Cu (0) while oxidizing Fe0 to Fe (III). The rate of reduction can be expressed by pseudo-second-order reaction kinetics. The rate constants increased with increasing iron loading and initial concentration at pH 6, while the adsorption of Cr (VI) and Cu (II) was found to be endothermic and exothermic, respectively. The apparent activation energies for Cr (VI) and Cu (II) were found to be 71.99 and 18.38 kJ mol−1, respectively. X-ray photoelectron spectroscopy confirmed the reduction process. The equilibrium data could be well described by both Langmuir and Temkin isotherms for describing monolayer adsorption and chemisorption processes, respectively. Both film diffusion and intraparticle diffusion were found to be the rate-limiting steps from the analysis of an intraparticle diffusion model. Thus, the synthesized chitosan–Fe0-nanoparticle–carboxymethyl β-cyclodextrin beads can be a potential material for in situ remediation of contaminated surface and ground water
Investigation of Chromium Removal Efficacy from Tannery Effluent by Synthesized Chitosan from Crab Shell
No full textThe efficiency of chromium removal from tannery effluents using prepared crab shell chitosan was studied. Adsorption of Cr by chitosan was investigated at various contact times, pH values, adsorbent dosages, and temperatures. The amount of Cr adsorbed under different conditions was evaluated using atomic adsorption spectroscopy (AAS). Subsequently, the changes in the physicochemical parameters were also examined. It was found that the total dissolved solids (TDS), electrical conductivity (EC), and turbidity of the tannery effluent decreased significantly after treatment with crab shell chitosan. No significant changes were found after different soaking times; in most cases, the best adsorption was achieved within the first hour of treatment. On the other hand, the total organic carbon (TOC) and pH increased significantly after treatment with chitosan, possibly owing to dissolution of organic compounds from the adsorbent materials. The concentration of Cr was significantly reduced after treatment with chitosan under different treatment conditions. However, the highest amount of Cr was adsorbed within the first hour of contact. After studying different treatment conditions, it was found that maximum Cr removal from the tannery effluent was achieved at pH 3 (60 °C) using an adsorbent dose of 5 g/100 mL
Removal of Pollutants from Water by Using Single-Walled Carbon Nanotubes (SWCNTs) and Multi-walled Carbon Nanotubes (MWCNTs)
No full textWater crisis is one of the supreme challenges worldwide as clean water is the ultimate need for human civilization and all other life on earth. In the present study, continuous adsorption experiments were carried out in an adsorption column to survey the efficiency of the carbon nanotubes (CNTs) for removal of pollutants from water/wastewater in terms of physicochemical parameters, such as electrical conductivity, total dissolved solids (TDS), pH, chemical oxygen demand (COD) and total organic carbon (TOC), by using both single-walled carbon nanotubes and multi-walled carbon nanotubes. Sample solutions were allowed to flow in down-flow mode through the fixed-bed of CNTs. The CNTs column showed a reduction efficiency of electrical conductivity 80 % from effluent treatment plant (ETP) treated water sample, 69.23 % from raw effluent sample, and 53.33 % from the synthetic salt water sample. Similarly, the efficiency of TDS reduction was 78.61 % from raw effluent sample, 66.86 % from ETP treated water sample, and 62.02 % from the synthetic salt water sample. COD also reduced 84.71 % from raw effluent sample and 39.58 % from the ETP treated water sample. In case of TOC, the column showed a reduction efficiency of 85.88 % from the ETP treated water sample and 70.79 % from the raw effluent sample. These findings suggested that CNTs present a great potential in removal of pollutants in terms of physicochemical parameters from water/wastewater
Phytofiltration of arsenic and cadmium from the water environment using Micranthemum umbrosum(J.F. Gmel) S.F. Blake as a hyperaccumulator
No full textCytotoxic effects of cadmium and zinc co-exposure in PC12 cells and the underlying mechanism
No full textCadmium (Cd2+) is a well studied inducer of cellular necrosis and apoptosis. Zinc (Zn2+) is known to inhibit apoptosis induced by toxicants including Cd2+ both in vitro and in vivo. The mechanism of Zn2+-mediated protection from Cd2+-induced cytotoxicity is not established. In this study, we aimed to understand the effects of Zn2+ on Cd2+-induced cytotoxicity and apoptosis using PC12 cells. Cell viability and DNA fragmentation assays in PC12 cells exposed to Cd2+ and/or Zn2+ revealed that Cd2+ (5 and 10 μmol/L) alone induced significant cell death, and co-exposure to Zn2+ (5, 10, and 100 μmol/L) for 48 h had a protective effect. Assessment of intracellular free sulfhydryl levels and lactate dehydrogenase activity suggested that Cd2+ (10 μmol/L) induced oxidative stress and disrupted cell membrane integrity. Addition of Zn2+ (10 and 100 μmol/L) reduced Cd2+-mediated cytotoxicity. Changes in expression of the apoptotic factors Bax, Bcl-2, Bcl-x, and cytochrome c were measured via western blot and expression of caspase 9 was detected via reverse transcriptase polymerase chain reaction. Western blots showed that Zn2+ (10 and 100 μmol/L) suppressed Cd2+-induced apoptosis (10 μmol/L) by reducing cytochrome c release into the cytosol, and downregulating the proapoptotic protein, Bax. In addition, expression of caspase 9 was lower in Cd2+ (5 μmol/L)-treated PC12 cells when co-treated with Zn2+ (2 and 5 μmol/L). These findings suggest that the effective inhibition of Cd2+-induced apoptosis in PC12 cells by Zn2+ might be due to suppression of mitochondrial apoptosis pathway and inhibition of Cd2+-induced production of reactive oxygen species
Removal of Cadmium and Chromium Ions Using Modified α, β, and γ-Cyclodextrin Polymers
No full textThe adsorption of cadmium and chromium from aqueous solutions with epichlorohydrin cross-linked α, β, and γ-cyclodextrin polymers (CDPs) was investigated under a wide range of experimental conditions including pH values, metal concentration, and CDP amounts. Recent studies have shown that α, β, and γ CDPs follow the Freundlich, Langmuir, and Brunauer-Emmett-Teller models and are capable of reducing heavy metal ion concentrations in water to desirable levels with enhanced sorption capabilities. The removal of cadmium and chromium achieved equilibrium in 4 h. The pH of effective cadmium removal was 6.5 to 7.5, and phosphate buffer favored the removal of cadmium in the presence of potassium ion. Chromium removal was optimal at pH 3.6 to 6.5. Current technologies can remove 99% cadmium ions from solution, yet this process is not very efficient. Furthermore, a small amount of CDPs can remove large quantities of heavy metal ions and can then be regenerated with acid for reuse. The present results are promising for using inexpensive CDPs as a low-cost material that is effective in remediating waters contaminated with heavy metal species. The sorption kinetics of CDPs along with the conditions to adsorb cadmium and chromium are reported here for the first time
Potential of Micranthemum umbrosum for phytofiltration of organic arsenic species from oxic water environment
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